Textile fibers comprising perfluoroalkanoyl esters of cellulose and process of making the same



TEXTILE FIBERS COMPRISING PERFLUORO- ALKANOYL ESTERS OF CELLULOSE AND PROCESS OF MAKING THE SAME Leon Sega], Metairie, and Leopold Loeb, Kazuo H. Takemura, and Frederick J. Philips, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed June 15, 1955, Ser. No. 515,797

9 Claims. (Cl. 8-120) (Granted under Title 35, US. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to perfiuoroalkanoyl esters of cellulose wherein the alkanoyl radical'contains from 2 to carbon atoms, and provides such esters in fibrous form and processes for their preparation.

A primary object of the present invention is to provide such esters in the form of fibers which are adapted for use in textiles. A further object is to provide an esterification process that can be employed to esterify cellulose textile fibers with perfiuoroalkanoic acids without destroying the properties of the fibers. A further object is to provide a process of modifying the properties of cellulose textile fibers to impart or enhance properties such as a resistance to wetting by liquids of all kinds, increased elasticity, and increased resistance to burning, and the like.

In general, in accordance with the present invention, a cellulose textile fiber is esterified with an esterifying agent of a perfluoroalkanoic acid wherein the alkanoyl radical contains from 2 to 10 carbon atoms until perfluoroalkanoyl esters of cellulose in textile fiber form are produced. In carrying out the process of the invention, the esterification is accomplished by a reaction, at a tem-, perature of about from 50 C. to 90 C., between the free hydroxyl groups of the cellulose molecules and the perfluoroalkanoic acid esterifying agent, which may be the perfluoroalkanoic acid itself, the anhydride thereof, or the acyl halide thereof, in the presence of a quantity of a normally liquid heterocyclic tertiary aromatic amine, such as pyridine, sufficient to dissolve the esterifying agent and to neutralize acidic reaction products to their respective amine salts, the esterification reaction being carried out until perfluoroalkanoyl esters of cellulose are produced.

The resulting perfluoroalkanoyl ester of cellulose retains the textile fibrous structure of the starting cellulose textile fiber, has a degree of substitution ranging from 1 to 3 perfiuoroalkanoyl groups per anhydroglucose unit of the cellulose, and is characterized in that it is resistant to wetting.

The fibrous cellulose esters of the invention are particularly useful in the production of protective fabrics and the like where a resistance to Wetting, and/or, elastic, thermoplastic, flame resistant, and the like properties, are desirable. The esters of the lower perfluoroalk-anoic acids containing a relatively high proportion of perfiuoroalkanoyl radicals tend to be soluble in organic solvents such as acetone, and are particularly useful in the production of surface coatings in which a resistance to wetting, and/ or, elastic, fiame resistant, and the like properties, is desired Yarns and fabrics consisting essentially of the 1 States Patent alkanoic acid wherein the alkanoyl radical contains from 2 to 10 carbon atoms can be employed in the present process. Acids whose esterifying agents can be employed include perfiuoroacetic, perfiuorobutyric, perfluorooctanoic, perfiuorodecanoic, perfluoroglutaric, and perfiuorosuccinic acid.

The esterifying agent can be one or more of the alcohol esterifying agents of acids, such as the free acid, the acid anhydride, or the acyl halide of the acid. The employment of the anhydrides of'straight chain monocarboxylic perfiuoroalkanoic acids of from about 2 to 8 carbon atoms is preferred.

In reacting the cellulosic fibers with the esterifying agent of a perfiuoroalkanoic acid, substantially any of the procedures and apparatus usually employed in the esterification of cellulose can be employed. 1

Particularly where the process is used to chemically modify the cellulose fibers, the perfiuoroalkanoic acid esterifying agent is preferably dissolved in a liquid tertiary organic amine. As they are dissolved in the amine, acidic esterifying agents and/or any acidic products of the esterification reaction are, of course, partially or wholly, converted to their respective amine salts. The esterification reaction is preferably accomplished by contacting the cellulose material with such a solution at a temperature above the freezing point of the solution and below a temperature at which an undesirable amount of cellulose degradation occurs. In general, the use of a heterocyclic tertiary aromatic amine, such as pyridine, or the like amines, of which pyridine is especially suitable, and a reaction temperature of from about 50 to C., is preferred. The contacting of the fibers with the solution can be accomplished by immersing the fibers in the solution. The fibers can be reacted with the solution with which they are in contact by maintaining the fibers immersed in the solution at the reaction temperature.

Where the esterificati'on is conducted in the presence of an organic amine, the amount of amine present can be varied widely. The reaction can be conducted by wetting the fibers with the amine and reacting the wet fibers with the esterifying agent. In general, it is preferable to have present enough amine (a) to dissolve the esterifying agent, and (b) to neutralize any acid formed in the course of the esterification reaction. Where the esterifying agent used is an anhydride or an acyl halide, the use of from about 1 to 10 parts of amine per part of anhydride is preferred.

The extent of reaction, and thus the degree of substitution, ie the number of the three reactive hydroxyls per anhydroglucose units which have been substituted, by replacing a hydrogen atom with an acyl radical, as indieated by the proportion of acyl groups per unit weight of the cellulose fibers, can be varied widely.

The degree of substitution can be varied as desired, primarily by (a) varying the proportion of esterifying agent in contact with the cellulose fibers during the esterification reaction, and (b) varying the time and temperafibrous esters are valuable as yarns and fabrics which,

ture of the esterification reaction.

Where the esterification reaction is conducted by maintaining the cellulose fibers immersed in a solution containing the esterifying agent at the reaction temperature, the proportion of esterifying agent in contact with the cellulosic material depends solely upon the ratio of the amount of the esterifying agent to the amount of cellulose. For example, the esterification of cellulose fibers by a reaction in which the cellulose fibers are immersed in a liquid organic amine containing dissolyed perfluoroalkanoic acid anhydride, a proportionof from' about 3 to 9 moles of anhydride per glucose unit is preferred.

, Where it is desired to esterify cellulose fibers to a rather low degree with a minimum alteration of the properties which adapt them for use in textiles, the cellulosefibers are preferably immersed in a normally liquid tertiary organic amine containing an amount of dissolved Perflu oroalkanoic acid anhydride providing from moles of anhydride per anhydroglucose .unit.

The esterification time and temperature can be controlled to. react substantially all of the available cellulose hydroxyl groups, or all of the perfiuoroalkanoic acid esterifying agent present, whichever is smaller. For example, in esterifications in which cotton fibers are reacted while they are immersed in an'excessof a liquid organic amine containing a perfiuoroalkanoicacid anhydride and maintained at temperatures ranging from 50 to 90 C., the degree of substitution can be varied from I to' substantially 3, using reaction times varying from 1 to hours; and reaction times of at least as long as 96 hours can be employed without a material destruction of the form in which the fibers are employed.

The following examples are illustrative of certain details of the invention.

In the following examples, where the anhydrides of the various perfiuoroalkanoic acids were used, the anhydrides were prepared from the corresponding acids by refluxing the acid under anhydrous conditions in the presence of slightly more than enough phosphorus pentoxide to react with the water eliminated in the conversion of the acid to it s anhydride.

A series of samples of cotton fibers, in the indicated forms, were esterified by reacting the fibers, while they were immersed in the indicated pyridine solutions containing the anhydridcs of the indicated acids, for the indicated reaction times and temperatures. The esterified fibers, excepting the acetate, were washed free of the reactant solution with pyridine and acetone (hexane being used with the acetate) and dried at from about 26 to 28 C. (room temperature) for several hours, conveniently overnight.

Example 1 A 0.52 gm. skein of kier-boiled, loose twist, singles cotton yarn which had been presoaked in mls. of pyridine was reacted with 39.4 gms. of perfluorobutyric anhydride in 40 mls. of pyridine at from 80 to 90 C. for about 96 hours.

The washed and dried product was a skein of yarn consisting essentially of perfluorobutyryl cellulose esters in the form of fibers having a degree of substitution of from about 2 to 3 (as indicated by a weight increase of 3.81 times the original weight). The product was elastic and V strongly resistant toward wetting by any chemically inert liquid. It was also flame resistant; it would not support combustion, and when it was held in a flame, it would melt but would not burn. 7

Example 2 A 1.6 gm. swatch of 80 x 80 cotton print cloth which had been boiled and bleached was reacted with 20.0 gms. of perfluorobutyric anhydride in 30 mls. of pyridine at a temperature of from 60 to 70 C. for about 24 hours.

The washed and dried reaction product was a cloth consisting essentially of perfluorobutyryl cellulose esters in the form of fibers having. a degree of substitution of about 3 to 4.5

4 Example 3 A 1.72 gm. swatch of 8.5 oz. cotton sateen was reacted with 39.9 gms. of perfiuorobutyric anhydride in 40 mls. of pyridine at from 60 to 70 C. for about 19 hours.

The washed and dried product was a cloth consisting essentially of perfluorobutyryl cellulose esters in the form of fibers having a degree of substitution of from about 1 to 2 (as indicated by a weight increase of 2.92 times the original weight). The product exhibited the properties of the product described in Example 1, differing in that it displayed high shrinkage.

Example 4 A 1.69 gm. swatch of 8.5 02. cotton sateen was reacted with 32.0 gms. of perfluorooctanoic anhydride in 35.0 mls. of pyridine at from 60 to 70 C. for about 24 hours.

I The washed and dried. product was a cloth consisting essentially of perfiuorooctanoyl cellulose esters in the form of fibers having a degree of substitution of from about 1 to 2 (as indicated by a weight increase of 5.16 times the original weight). The product exhibited the properties of the product described in Example 3.

Example 5 A 2.02 m. skein of kier-boiled, loose twist, singles cotton yarn and a 2.34 gm. swatch of 80 x 80 cotton print cloth which had been boiled and bleached were reacted together with 17.4 gms. of perfiuoroacetic anhydride in 90 mls. of pyridine at about 50 C. for about 2 hours.

' The washed and dried products were (a) a skein of yarn consisting essentially of perfluoroacetyl cellulose esters in the form of fibers having a degree of substitution of lto 2 (as indicated by a weight increase of 1.79 times the original weight) and (b) a cloth consisting essentially of perfiuoroacetyl cellulose esters in the form of fibers having a degree of substitution of about 1 (as indicated by a weight increase of 1.56 times the original weight). Both products exhibited the properties of the productdescribed in Example 1.

Example 6 A 2.35 gm. skein of kier-boiled, loose twist, singles cotton yarn and a 2.22 gm. swatch of 80 x 80 cotton print cloth which had been boiled and bleached were reacted together with 18.0 gms. of n-heptafluorobutyryl chloride in 90 mls. of pyridine at room temperature for about 12 hours. (While the reaction was conducted overnight for convenience it appeared that the reaction was completed within an hour.) I

The washed and dried products were.(a) a skein of yarn consisting essentially of perfluorobutyryl cellulose from about 1 to 2 (as indicated by a weight increase of 2.62. times theoriginal weight). The product exhibited the properties of the product described in Example w i esters in the form of fibers having a weight increase such as to indicate complete esterification of the cellulose and (b) a cloth consisting essentially of perfluorobutyryl cellulose esters in the form of fibers having a degree of sub stitution of about'2 to 3 as indicated by the weight increase. Both products exhibited the properties of the product describer in Example 1.

We claim:

1. A textile fiber comprising a perfiuoroalkanoyl ester of cellulose wherein the alkanoyl radical contains from 2 to 10 carbon atoms, said fiber having a degree of substitution ranging from 1 to 3 perfluoroalkanoyl groups per anhydroglucose unit of the cellulose and being characterized in that it is resistant to wetting.

2. A textile fiber comprising a perfluoroacetyl ester of cellulose, said fiber having a degree of substitution ranging from 1 to 3 perfluoroacetyl groups per anhydroglucose unit of the cellulose-and being characterized in that it is resistantto wetting.

c 3. A textile fiber comprising 'alPerfluOrobutyrylester ranging from 1 to 3 perfluorobutyryl groups per anhydroglucose unit of thevcellulose and being characterized in that it is resistant to wetting.

4. A textile fiber comprising a perfluorooctanoyl ester of cellulose, said fiber having a degree of substitution ranging from 1 to 3 perfluorooctanoyl groups per anhydroglucose unit of the cellulose and being characterized in that it is resistant to wetting.

5. A process of converting a cellulose textile fiber to a cellulose textile fiber containing perfluoroalkanoyl radicals attached to the cellulose molecules, comprising reacting, at a temperature of about from 50 C. to 90 C., a cellulose textile fiber with an esterifying agent of a perfiuoroalkanoic acid wherein the alkanoyl radical contains from 2 to 10 carbon atoms and which agent is selected from the group consisting of the said acid, its anhydride, and its acyl halide, in the presence of a quantity of a normally liquid heterocyclic tertiary aromatic amine suflicient to dissolve the esterifying agent and to neutralize acidic reaction products to their respective amine salts, said reaction 'being carried out until perfluoroalkanoyl esters of cellulose in the form of a textile fiber is produced, the thus-produced textile fiber having a degree of substitution ranging from 1 to 3 perfluoroalkanoyl groups per anhydroglucose unit of the cellulose and being characterized in that it is resistant to wetting.

6. The process of claim 5 wherein the esterifying agent is perfluoroacetic anhydride.

7. The process of claim 5 wherein the esteritying agent is perfiuorobutyric anhydride.

8. The process of claim 5 wherein the esterifying agent is perfiuorooctanoic anhydride.

9. The process of claim 5 wherein the amine is pyridine.

References Cited in the file of this patent UNITED STATES PATENTS 1,698,049 Clarke Jan. 8, 1929 1,739,210 Clarke Dec. 10, 1929 1,880,808 Clarke Oct. 4, 1932 1,969,468 Malm Aug. 7, 1934 2,170,024 Heckert i Aug. 22, 1939 2,225,589 Haussman Dec. 17, 1940 FOREIGN PATENTS 439,880 Great Britain Dec. 17, 1935 

5. A PROCESS OF CONVERTING A CELLULOSE TEXTILE FIBER TO A CELLULOSE TEXTILE FIBER CONTAINING PERFLUOROALKANOYL RADICALS ATTACHED TO THE CELLULOSE MOLECULES, COMPRISING REACTING, AT A TEMPERATURE OF ABOUT FROM 50*C. TO 90*C., A CELLULOSE TEXTILE FIBER WITH AN ESTERIFYING AGENT OF A PERFLUUOROALKANOIC ACID WHEREIN THE ALKANOYL RADICAL CONTAINS FROM 2 TO 10 CARBON ATOMS AND WHICH AGENT IS SELECTED FROM THE GROUP CONSISTING OF THE SAIE ACID, ITS ANHYDRIDE, AND ITS ACYL HALIDE, IN THE PRESENCE OF A QUANTITY OF A NORMALLY LIQUID HETEROCYCLIC TERTIARY AROMATIC AMINE SUFFICIENT TO DISSOLVE THE ESTERIFYING AGENT AND TO NEUTRALIZE ACIDIC REACTION PRODUCTS TO THEIR RESPECTIVE AMINE SALTS, SAID REACTION CARRIED OUT UNTIL PERFLUOROALKANOYL ESTERS OF CELLULOSE IN THE FORM OF A TEXTILE FIBER IS PRODUCED, THE THUS-PRODUCED TEXTILE FIBER HAVING A DEGREE OF SUBSTITUTION RANGING FROM 1 TO 3 PERFLUOROALKANOYL GROUPS PER ANHYDROGLUCOSE UNIT OF THE CELLULOSE AND BEING CHARACTERIZED IN THAT IT IS RESISTANT TO WETTING. 